Charles McGowin, Evan Hughes & Neville Holt, EPRI
The potential of the biomass
gasification combined cycle (BGCC) approach for efficient and fuel-flexible use of biomass
for power generation led the Global Environment Facility (GEF) and The World Bank to
consider a pilot demonstration program in Brazil
As part of Phase II the World Bank contracted EPRI to
undertake an economic and risk evaluation of the Brazil BIG-GT project. The risk
evaluation perfumed by EPRI was conducted in order to assess whether biomass
gasification/combined cycle technology will eventually become competitive with other new
and evolving electricity supply resources available in northeastern Brazil.
The results of the evaluation are described.
The Brazil Project
Brazil Biomass Integration Gasification – Gas turbine
(BIG-GT Project)
The potential of the biomass gasification combined cycle (BGCC)
approach for efficient and fuel-flexible use of biomass for power generation led the
Global Environment Facility (GEF) and The World Bank to consider a pilot demonstration
program in Brazil. Earlier studies by Princeton University and Companhia Hidroeletrica do
Sao Francisco (CHESF) indicate that development and commercialization of reliable and
efficient biomass gasification-combined cycle technology could make it possible to develop
considerable electricity supply capacity in northeastern Brazil at costs below the
marginal system costs (Ref. 1). The electricity supply potential is estimated to be about
20,000 MWe.
Project Objectives
The key development objectives of the Brazil BIG-GT project are:
• Short-term objective: To establish a
globally-replicable prototype unit on a commercial scale for the cogeneration of
electricity based on the gasification of wood chips or sugarcane bagasse. No native
forests will be used in fulfilling this objective.
• Long-term objective: To reduce global warming by
lowering CO2 emissions from fossil fuels which would be produced by conventional thermal
generation.
The environmental and social objectives of the project include
employment and income growth in rural areas, sustainable development, increased private
capital investment in the power sector, economic support to industries that already use
biomass, verification of the benefits of afforestation for energy production and
decentralized electricity generation, and creation of long-term programs for wood and
sugarcane production.
It is anticipated that covering up to five per cent of the land
area of northeastern Brazil with energy plantations would generate $1.7 billion of
investment capital, result in construction of 10 to 20 BIG-GT power plants each year, and
create 12,000 new jobs per year needed to develop, operate, and maintain the energy
plantations and power plants.
Conceptual designs and cost estimates were produced for two
different biomass gasification technologies in combination with the General Electric
LM-2500 aeroderivative gas turbine:
(1) the atmospheric fluidized bed combustion gasification
technology offered by TPS Termiska Processor AB, using cold quench wet scrubbing to clean
up of the product gas; and
(2) the pressurized fluidized bed gasification technology offered
by Bioflow, a joint venture between A. Ahlstrom Corporation in Finland and Sydkraft AB of
Sweden, using hot gas ceramic filters to clean up the product gas.
Phase I resulted in the selection of the TPS Termiska atmospheric
fluidized bed combustion technology for the project (Ref. 2).
Economic and Risk Evaluation
As part of Phase II the World Bank contracted EPRI to undertake
an economic and risk evaluation of the Brazil BIG-GT project. The risk evaluation perfumed
by EPRI was conducted in order to assess whether biomass gasification/combined cycle
technology will eventually become competitive with other new and evolving electricity
supply resources available in northeastern Brazil.
The overall objective of the risk evaluation was to assess: (1)
the impact of World Bank/GEF funding of the Brazil biomass gasification demonstration
project on the commercialization timetable of the technology; and (2) the likelihood that
biomass gasification/combined cycle technology will ultimately deliver power to
northeastern Brazil at a lower cost than other new and evolving candidate electricity
supply options.
The risk evaluation by EPRI included the following: (1)
Identification of the candidate electricity supply options for the northeastern region of
Brazil; (2) deterministic analysis of the levelized delivered cost of electricity for each
of the supply options; (3) probabilistic analysis of biomass gasification-combined cycle
technology; and (4) decision analysis of the World Bank decision about whether to fund the
Brazil BIG-GT demo project.
The results indicated that biomass gasification, biomass
combustion, and wind turbines are likely to be competitive with other candidate power
supply options in northeastern Brazil after 2010, including oil- and gas-fired combined
cycle, coal gasification, gas- and oil-steam, hydro, and native and imported coal-steam.
The decision analysis indicated that the present value savings of a decision by the World
Bank to fund the project could reach $200 to $400 million in 2010, relative to a decision
not to fund the project. This assumes that the experience gained in the demo project would
lead to use of more advanced technology to build ten or more 100MW biomass gasification
plants in 2010 and each plant would realize life cycle present worth savings of $20 to $40
million.
BIG-GT Demonstration Plant
Process Description
The proposed BIG-GT demonstration plant will generate
approximately 40 MW of electricity and deliver approximately 32 MW of electricity to the
grid. The wood feed is chipped and dried (using waste heat)on-site. The dried wood chips
are fed to the air-blown fluidized bed gasifier (1.8 bar). The wood chips and residual
char are suspended by the upward flowing air injected at the bottom of the gasifier vessel
and by the product gases released by the gasification reactions. Solids that are entrained
with the product gases leaving the vessel are separated and removed by a cyclone separator
and reinjected into the gasifier.
Before passing to the gas turbine, the product gas is subjected
to a series of conditioning steps to remove tars, ammonia, and fine particulate that could
damage or otherwise adversely affect the gas turbine, including tar cracking, quench
scrubbing and gas compression.
Figure 1. Process Schematic of TPS Termiska Atmospheric
Pressure GIG-GT Demonstration Project (Ref. 3)
Demonstration Plant Performance
Table 1. Projected Performance and Fuel and Auxiliary Power
Consumption
|
Units |
Quantity |
% |
| Plant
Performance |
|
|
|
| Gross
Capacity |
MW |
40.40 |
100.0% |
| Auxiliary
Power |
MW |
8.14 |
20.1% |
| Net
Capacity |
MW |
32.26 |
79.9% |
| Annual
Capacity Factor |
% |
|
85% |
| Annual
Generation |
MWh/yr |
240,208 |
|
|
|
LHV Basis |
HHV Basis |
| Net
Thermal Efficiency |
% |
40.7% |
38.0% |
| Net
Plant Heat Rate |
kJ/kWh |
8,848 |
9,473 |
|
Btu/kWh |
8,389 |
8,982 |
| Biomass
Heat Content |
GJ/dry m ton |
18.4 |
19.7 |
|
MBtu/dmt |
17.4 |
18.7 |
| Fuel
Consumption |
|
Hourly |
Annual |
| Biomass
Fuel |
dry m ton |
15.52 |
115,562 |
| LPG |
kg |
6.0 |
44,700 |
| Diesel
Oil |
m ton |
0.10 |
72 |
| Auxiliary
Power Cons. |
|
|
|
| Gas
Compression |
MWh |
4.90 |
36.5 |
| BOP |
MWh |
3.24 |
24.1 |
Table 2. Projected Cost of Wood Stumpage, Harvesting,
Transport, and In-Plant Handling and Chipping
| Cost
Item |
US $/m ton (0% m) |
US $/GJ |
US $/MBtu |
% of Total |
Price of Wood on the Stump |
$13.75 |
$0.70 |
$0.74 |
35.6% |
Price of Cutting |
6.19 |
0.31 |
0.33 |
16.0% |
Price of in Field Transport |
5.57 |
0.28 |
0.30 |
14.4% |
Price of Cut Wood in the Field |
$25.51 |
$1.29 |
$1.37 |
66.0% |
Price of Loading |
4.02 |
0.20 |
0.22 |
10.4% |
Price of Freight |
4.33 |
0.22 |
0.23 |
11.2% |
Price of Wood at Gate before ST |
$33.86 |
$1.72 |
$1.81 |
21.6% |
Social Tax |
0.21 |
0.01 |
0.01 |
0.5% |
Social Tax |
0.69 |
0.03 |
0.04 |
1.8% |
Price of in Plant Wood Handling |
$34.75 |
$1.76 |
$1.86 |
2.3% |
Price of in Plant Wood Handling |
0.89 |
0.05 |
0.05 |
2.3% |
Price of Wood Chipping |
2.96 |
0.15 |
0.16 |
7.7% |
Total Price of Wood Delivered
to Dryer |
$38.60 |
$1.96 |
$2.07 |
100.0% |
Table 3. Fuel and Fixed and Variable O&M
Costs (85% capacity factor)
|
|
Annual Cost |
$/kW-yr |
$/MWh |
% of Total |
| Wood Fuel |
|
$3,936,981 |
$122.0 |
$16.39 |
52.3% |
| Auxiliary
Fuel |
|
|
|
|
| LPG |
|
$15,960 |
$0.49 |
$0.07 |
0.2% |
| Diesel Oil |
|
$338,037 |
$10.48 |
$1.41 |
4.5% |
Total
|
$353,997 |
$10.97 |
$1.48 |
4.7% |
| Variable
O&M |
|
|
|
|
| Dolomite/Areia |
$250,383 |
$7.76 |
$1.04 |
3.3% |
| Chemicals |
|
89,643.44 |
2.78 |
0.37 |
1.2% |
| Lubricants |
|
28,597.93 |
0.89 |
0.12 |
0.4% |
| Fuel
Handling |
250,915.90 |
7.78 |
1.04 |
3.3% |
| Ash
Disposal |
|
43,169.39 |
1.34 |
0.18 |
0.6% |
Total
|
|
$662,709 |
$20.54 |
$2.76 |
8.8% |
| Fixed
O&M |
|
$2,567,162 |
$79.6 |
$10.69 |
34.1% |
| Total
O&M and Fuel |
$7,166,853 |
$233.1 |
$31.31 |
100.0% |
Results
of the Risk Evaluation
EPRI used their "BIOPOWER" spreadsheet model for
sensitivity analyses to determine the parameters most critical in determining the
economics and the risks associated with biomass gasification power generation technology.
A "Tornado chart" (Figure 3) displays the relative importance of various
technical and economic parameters in changing the cost of the electric energy generated by
the BIG-GT power system.
The dominant parameters are total plant cost (i.e., the capital
cost), the discount rate (a non-technical, purely economic factor, not directly related to
the technology itself), and the availability/capacity factor (CF). The ranges of change in
the cost of electricity (COE) shown in Figure 3 are derived from both the judgement of the
likely range in the value of the parameter involved (e.g., total plant cost from a low of
$1830/kW to a high of $2180/kW for the year 2000 case) and from the importance of (i.e.,
sensitivity to) that parameter in the overall economic model that calculates the cost of
electricity (COE). In Figure 3, cost of electricity is expressed in $/MWh above or below a
base case cost of $92/MWh in the year 2000.
These results were then used in a probabilistic model to
calculate cumulative probability distribution functions for the COE in various future
years as the technology improves. (Figure 4 and Table 4)
Finally a decision analysis calculation was made to estimate the
benefits in risk reduction, and the related cost reduction, associated with the World Bank
and GEF continuing to cosponsor the Brazil biomass gasification power system project.
Figure 2. Tornado Chart
Figure 3: Cumulative Probability
Decision Analysis
The decision analysis addressed the potential outcomes of two
alternate World Bank decisions regarding funding of the Brazil BIG-GT demonstration
project:
1. World Bank decides to fund the demonstration project.
2. World Bank decides not to fund the demonstration project.
The decision analysis addressed the levelized delivered cost of
electricity (COE)for a 100 MW commercial biomass gasification power plant, constructed in
northeastern Brazil soon after 2010. The analysis focused on: the likely impact of the
possible World Bank funding decisions on construction of the demo plant; the resulting
experience gained by Brazilian scientific, agricultural, and industrial community; the
capability to construct, operate, and maintain a power plant using advanced technology in
both Brazil and other developing countries; and the resulting levelized delivered COE.
Figure 4 presents the decision tree developed for the decision
analysis. The decision tree displays the structural relationship between the decisions,
World Bank Funds Project, and World Bank Doesn’t Fund Project, and the uncertainty
variables, State of Technology used in 2010, Total Plant Cost, Biomass Fuel Cost, and
Annual Capacity Factor.
The State of Technology used in 2010 variable characterizes the
impact of the World Bank funding decision on the technology used to build a commercial
plant in 2010. It was assumed that a decision to provide World Bank funding of the project
would provide the capability for Brazil to develop and use more advanced technology in
2010 (possible outcomes: use 2020, 2015, or 2010 technology in year-2010 commercial
plants). Conversely, a decision not to provide World Bank funding would make it difficult
for Brazil to use even the technology expected to be commercially available in 2010
(possible outcomes: use 2010, 2005, or 2000 technology in year-2010 commercial plants).
Each branch of the tree represents a specific combination
of the four uncertainty variables, and all possible combinations of the variables are
addressed. There is one node associated with each uncertainty variable. Each node has
three branches, each corresponding to three values of the uncertainty variable and
probabilities of occurrence.
The decision tree was used to develop the cumulative probability
distributions of the levelized delivered cost of electricity in 2010 shown in Figure 5,
one for each potential World Bank decision.
Key Findings
- The cumulative probability curves suggest that, if the World Bank
decides to fund the Brazil Biomass Integrated Gasification/Gas Turbine Project, the
expected levelized cost of electricity of a biomass gasification power plant will be about
$12/MWh lower for plants built in 2010, than if the decision is made not to provide the
funding.
Figure 5. Cumulative Probability Distributions Levelized Delivered COE vs. World
Bank Funding Decision Outcome
• The Brazil Biomass Integrated Gasification-Gas
Turbine (BIG-GT)demonstration project would play an important role in the progress toward
lower cost biomass power, especially in developing countries.
• The experience gained in the project by the Brazilian
scientific, technical, agricultural, and industrial communities would provide the know-how
and capability to use more advanced technology and probably accelerate the introduction of
commercial biomass gasification-combined cycle power plants in Brazil after the year 2000.
• The deterministic analysis suggests that biomass
gasification and direct combustion power plants offer potential to supply electricity to
meet the growing power demand in northeastern Brazil after the year 2000 at a delivered
life-cycle cost that is lower than or competitive with the cost of all other candidate
electricity supply options, including natural gas-combined cycle.
• The probabilistic analysis of biomass gasification
combined cycle power plants suggests that there is a high probability that biomass
gasification and direct combustion power plants will deliver electricity to northeastern
Brazil at a cost that is lower than or competitive with the cost for all other electricity
supply options after the year 2010.
• The decision analysis of the World Bank funding decision
suggests that World Bank funding will contribute significantly to Brazil’s capability
to deploy biomass gasification power plants in Brazil after the year 2010 and would reduce
the delivered cost of electricity from the plants.
References
1. Elliott, Philip and Roger Booth, "Brazilian Biomass
Power Demonstration Project", Special Project Report, Shell International Petroleum
Company, London, 1993.
2. "Brazil Biomass Integrated Gasification/Gas Turbine
Project," Global Environment Facility, United Nations Development Program, New York,
1993.
3. "Renewable Energy Technology Characterizations,"
Joint Report, EPRI and U.S. Department of Energy, EPRI TR-109496, December 1997.
4. "Brazil Hydro and Thermal Power Sector Study," Joint
United Nations Development Program/World Bank, Report No. 197/97, September 1997.
5. "BIOPOWER: Biomass and Waste Fuel Power Plant Performance
and Cost Model," EPRI TR-101774, March 1985.
6. "TAG™ - Technical Assessment Guide, Volume 1:
Electricity Supply—1993," Revision 7, Electric Power Research Institute, Palo
Alto, CA, EPRI/TR-102276-V1R7, 1993.
